Hearing prosthesis with a piezoelectric actuator

ABSTRACT

A hearing prosthesis including an actuator. The actuator includes a material that deforms in response to an electrical signal and that is adapted to, upon implantation in a recipient, transmit vibrations representative of a sound signal to an organ of the recipient, wherein the material is at least partially exposed to at least one of body tissue and fluid of the recipient.

BACKGROUND

1. Field of the Invention

The present invention relates generally to hearing prostheses, and moreparticularly, to a hearing prosthesis with a piezoelectric actuator.

2. Related Art

Hearing loss, which may be due to many different causes, is generally oftwo types: conductive and sensorineural. Sensorineural hearing loss isdue to the absence or destruction of the hair cells in the cochlea thattransduce sound signals into nerve impulses. Various hearing prosthesesare commercially available to provide individuals suffering fromsensorineural hearing loss with the ability to perceive sound. Forexample, cochlear implants use an electrode array implanted in thecochlea of a recipient to bypass the mechanisms of the ear. Morespecifically, an electrical stimulus is provided via the electrode arrayto the auditory nerve, thereby causing a hearing percept.

Conductive hearing loss occurs when the normal mechanical pathways thatprovide sound to hair cells in the cochlea are impeded, for example, bydamage to the ossicular chain or ear canal. Individuals suffering fromconductive hearing loss may retain some form of residual hearing becausethe hair cells in the cochlea may remain undamaged.

Individuals suffering from conductive hearing loss typically receive anacoustic hearing aid. Hearing aids rely on principles of air conductionto transmit acoustic signals to the cochlea. In particular, a hearingaid typically uses an arrangement positioned in the recipient's earcanal or on the outer ear to amplify a sound received by the outer earof the recipient. This amplified sound reaches the cochlea causingmotion of the perilymph and stimulation of the auditory nerve.

In contrast to hearing aids, certain types of hearing prosthesescommonly referred to as bone conduction devices, convert a receivedsound into mechanical vibrations. The vibrations are transferred throughthe skull to the cochlea causing generation of nerve impulses, whichresult in the perception of the received sound. Bone conduction devicesmay be a suitable alternative for individuals who cannot derivesufficient benefit from acoustic hearing aids, cochlear implants, etc.

Other types of hearing prostheses commonly referred to as middle-earimplants, also convert received sound into vibrations. The vibrationsare delivered to the middle ear or inner ear, and are thereaftertransferred to the cochlea causing generation of nerve impulses, whichresult in the perception of the received sound.

SUMMARY

In accordance with one aspect of the present invention, there is ahearing prosthesis comprising, an actuator including a material thatdeforms in response to an electrical signal and that is adapted to, uponimplantation in a recipient, transmit vibrations representative of asound signal to an organ of the recipient, wherein the material is atleast partially exposed to at least one of body tissue and fluid of therecipient.

In accordance with another aspect of the present invention, there is ahearing prosthesis comprising actuator means for deforming in accordancewith an electrical sound signal to vibrate a hearing organ of arecipient, wherein the means is at least partially exposed to at leastone of internal body tissue and fluid of the recipient.

In accordance with yet another aspect of the present invention, there isa transducer, comprising a material that generates electricity whendeformed, wherein the material is adapted to be at least partiallyexposed to at least one of body tissue and fluid of the recipient.

In accordance with another aspect of the present invention, there is amethod of imparting vibrational energy to bone, the method comprisingdeforming a deformable material in response to an electric signalapplied thereto, and imparting vibrational energy resulting from thedeformation of the deformable material directly from the deformablematerial to the bone.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described below with referenceto the attached drawings, in which:

FIG. 1 is a perspective view of an exemplary bone conduction device inwhich embodiments of the present invention may be implemented;

FIG. 2 is a functional block diagram of a bone conduction device inaccordance with an embodiment of the present invention;

FIG. 3A is a flowchart illustrating the conversion of an input sound toskull vibration in a bone conduction device according to an embodimentof the present invention;

FIGS. 3B-3D are schematic diagrams illustrating an exemplary principleof operation of a piezoelectric material subjected to an electricalsignal;

FIG. 4 is a schematic diagram presenting an exemplary embodiment of anactive transcutaneous bone conduction device according to the presentinvention;

FIG. 5A is a schematic diagram presenting an exemplary embodiment of anactuator used in an active transcutaneous bone conduction deviceaccording to the present invention;

FIG. 5B is a schematic diagram presenting an alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 5C is a schematic diagram presenting another alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 5D is a schematic diagram presenting another alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 5E is a schematic diagram presenting another alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 6A is a schematic diagram presenting another alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 6B is a schematic diagram presenting another alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 6C is a schematic diagram presenting another alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 6D is a schematic diagram presenting another alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 6E is a schematic diagram presenting another alternative exemplaryembodiment of an actuator used in an active transcutaneous boneconduction device according to the present invention;

FIG. 7 is a schematic diagram presenting an exemplary embodiment of anactuator used in a combination active transcutaneous bone conductiondevice/percutaneous bone conduction device according to the presentinvention; and

FIG. 8 presents a chart including exemplary dimensions of a componentused in an exemplary embodiment of the present invention.

FIG. 9 is a perspective view of an exemplary middle-ear implant in whichembodiments of the present invention may be implemented; and

FIG. 10 is a perspective view of an exemplary middle-ear implant inwhich embodiments of the present invention may be implemented.

FIG. 11A is a perspective view of an exemplary actuator usable withhearing prostheses;

FIG. 11B is a perspective view of an exemplary actuator according to anembodiment of the present invention;

FIG. 11C is a perspective view of another exemplary actuator accordingto an embodiment of the present invention;

FIG. 12 is a perspective view of a hearing prosthesis utilizing animplantable microphone according to an embodiment of the presentinvention; and

FIG. 13 is a perspective view of an implantable electricity generatoraccording to an embodiment of the present invention.

DETAILED DESCRIPTION

Aspects of the present invention are generally directed to a hearingprosthesis actuator having a piezoelectric material to be implanted in arecipient to be at least partially exposed to the recipient's bodytissue and/or fluid. That is, there is no housing or other type ofbarrier forming a hermetic seal between the piezoelectric material andthe organic environment in which it is implanted. In exemplaryembodiments, the piezoelectric material is barium titanate (BaTiO₃)and/or strontium titanate (SrTiO₃).

Because the piezoelectric material is biocompatible, no housing isinterposed between the actuator and the organic environment of therecipient, enabling the material to directly osseointegrate to tissue(e.g., bone) of the recipient. This reduces losses of vibrational energyas vibrations are transferred from the actuator to the tissue.

By “biocompatible,” it is meant that the piezoelectric material is amaterial that would meet regulatory approval by at least one of theUnited States, Japan and the European Union for implantation into ahuman such that the material would be at least partially exposed for along term to the recipient's body tissue and/or fluid.

FIG. 1 is a perspective view of an active transcutaneous bone conductiondevice 100 in which embodiments of the present invention may beimplemented. As shown, the recipient has an outer ear 101, a middle ear102 and an inner ear 103. Elements of outer ear 101, middle ear 102 andinner ear 103 are described below, followed by a description of boneconduction device 100.

In a fully functional human hearing anatomy, outer ear 101 comprises anauricle 105 and an ear canal 106. A sound wave or acoustic pressure 107is collected by auricle 105 and channeled into and through ear canal106. Disposed across the distal end of ear canal 106 is a tympanicmembrane 104 which vibrates in response to acoustic wave 107. Thisvibration is coupled to oval window or fenestra ovalis 110 through threebones of middle ear 102, collectively referred to as the ossicles 111and comprising the malleus 112, the incus 113 and the stapes 114. Theossicles 111 of middle ear 102 serve to filter and amplify acoustic wave107, causing oval window 110 to vibrate. Such vibration sets up waves offluid motion within cochlea 139. Such fluid motion, in turn, activateshair cells (not shown) that line the inside of cochlea 139. Activationof the hair cells causes appropriate nerve impulses to be transferredthrough the spiral ganglion cells and auditory nerve 116 to the brain(not shown), where they are perceived as sound.

FIG. 1 also illustrates the positioning of bone conduction device 100relative to outer ear 101, middle ear 102 and inner ear 103 of arecipient of device 100. As shown, bone conduction device 100 ispositioned behind outer ear 101 of the recipient. The bone conductiondevice 100 comprises an external component 140 and implantable component150. The bone conduction device 100 includes a sound input element 126to receive sound signals. Sound input element may comprise, for example,a microphone, telecoil, etc. In an exemplary embodiment, sound inputelement 126 may be located, for example, on or in bone conduction device100, or on a cable extending from bone conduction device 100. The soundinput element 126 may be part of the external component 140 as shown, ormay be part of the implantable component 150 (e.g., it may besubcutaneously implanted in the recipient). Sound input element 126 mayalso be a component that receives an electronic signal indicative ofsound, such as, for example, from an external audio device. For example,sound input element 126 may receive a sound signal in the form of anelectrical signal from an MP3 player electronically connected to soundinput element 126.

Bone conduction device 100 comprises a sound processor, a vibratingpiezoelectric actuator and/or various other operational components. Moreparticularly, sound input device 126 (e.g., a microphone) convertsreceived sound signals into electrical signals. These electrical signalsare processed by the sound processor. The sound processor generatescontrol signals which cause the actuator to vibrate. In other words, theactuator converts the electrical signals into mechanical motion toimpart vibrations to the recipient's skull.

As noted above, bone conduction device 100 is an active transcutaneousbone conduction device. That is, at least one active component (e.g. thepiezoelectric actuator) 152 is implanted beneath the skin and is thuspart of the implantable component 150. That is, implantable component150 is configured to generate stimulation mechanical force that isconducted via one or more recipient's bones to produce an auditorystimulation. Additional details of such embodiments are described ingreater detail below.

As described below, external component 140 may comprise a soundprocessor and signal transmitter, while implantable component 150 maycomprise a signal receiver and/or various other electroniccircuits/devices contained in implantable housing 154. As may be seen,implantable housing 154 is in electrical communication with activecomponent 152 via electrical leads 156. These features and otherfeatures of the implantable component 150 are discussed in greaterdetail below.

In accordance with embodiments of the present invention, the activecomponent 152 is in direct contact with bone 136. As will be discussedin greater detail below, the active component 152 may be a piezoelectricactuator that is osseointegrated to the bone 136.

A functional block diagram of one embodiment of active transcutaneousbone conduction device 100, referred to as active transcutaneous boneconduction device 200, is shown in FIG. 2. In the illustratedembodiment, a sound 207 is received by a sound input element 226 ofexternal device 240, the sound input element 226 corresponding to soundinput element 126 detailed above. In some embodiments, sound inputelement 226 is a microphone configured to receive sound 207, and toconvert sound 207 into an electrical signal 222. As described below, inother embodiments sound 207 may be received by sound input element 226already in the form of an electrical signal 222 and thus, in someembodiments, it is not converted by sound input element 226.

As shown in FIG. 2, electrical signal 222 is output by sound inputelement 226 to an electronics module 204. Electronics module 204 isconfigured to convert electrical signal 222 into an adjusted electricalsignal 224. As described below in more detail, electronics module 204may include a sound processor, control electronics, and a variety ofother elements. FIG. 2 also illustrates a power module 210. Power module210 provides electrical power to one or more components of activetranscutaneous bone conduction device 200. For ease of illustration,power module 210 has been shown connected only to interface module 212and electronics module 204. However, it should be appreciated that powermodule 210 may be used to supply power to any electrically poweredcircuits/components of active transcutaneous bone conduction device 200.

Active transcutaneous bone conduction device 200 further includes aninterface module 212 that allows the recipient to interact with device200. For example, interface module 212 may allow the recipient to adjustthe volume, alter the speech processing strategies, power on/off thedevice, etc. Interface module 212 communicates with electronics module204 via signal line 228.

In the embodiment illustrated in FIG. 2, sound input element 226,electronics module 204, power module 210 and interface module 212 may beintegrated in a single housing, all of these components collectivelycorresponding to external device 140 detailed above. However, it shouldbe appreciated that in certain embodiments of the present invention, oneor more of the illustrated components may be housed in separate ordifferent housings. Similarly, it should also be appreciated that insuch embodiments, direct connections between the various modules anddevices are not necessary and that the components may communicate, forexample, via wireless connections.

As may be seen from FIG. 2, electronics module 204 comprises a soundprocessor 227, signal generator 242 and control electronics 246, signalgenerator 242 being in electrical communication with control electronics246 via signal line 230. Sound input element 226 is also in electricalcommunication with control electronics 246 via signal line 216. Asexplained above, in certain embodiments sound input element 226comprises a microphone configured to convert a received acoustic signalinto electrical signal 222. FIG. 2 also shows that sound processor 227is in electrical communication with control electronics 246 via signalline 232.

In embodiments of the present invention, electrical signal 222 is outputfrom sound input element 226 to sound processor 227. Sound processor 227uses one or more of a plurality of techniques to selectively process,amplify and/or filter electrical signal 222 to generate a processedsignal 229. In certain embodiments, sound processor 227 may comprisesubstantially the same sound processor as is used in an air conductionhearing aid. In further embodiments, sound processor 227 comprises adigital signal processor.

Processed signal 229 is provided to signal generator 242. Signalgenerator 242 outputs the adjusted electrical signal 224 to atransmitter module which comprises a transmission device such as, forexample, a transmitter coil 206 that, in some embodiments, establishesan inductive transcutaneous link with a receiver coil in the implantablecomponent 150. More specifically, adjusted electrical signal 224 istransmitted via transmitter coil 206 of the transmitter module to areceiver coil (not shown) of receiver module 254 of the implantablecomponent 250, which, in some embodiments, corresponds to implantablecomponent 150 detailed above with respect to FIG. 1. In someembodiments, receiver module 254 corresponds to or is in electricalcommunication with implantable housing 154 detailed above with respectto FIG. 1. Actuator 260, which is in electrical communication withreceiver module 254 generates mechanical vibration that is communicatedthrough the recipient's bone in order to provide stimulation to theauditory nerve of the recipient.

For ease of description the signal supplied by signal generator 242 viathe transmitter module to actuator 260 has been referred to as anadjusted electrical signal 224. In some embodiments, it may be anactuator control signal. In some embodiments, the adjusted electricalsignal 224 may comprise an unmodified version of processed signal 229,which may be further processed in implantable component 250 in otherembodiments of the present invention.

In one embodiment of the present invention, actuator 260 generates anoutput force that causes movement of the cochlea fluid so that a soundmay be perceived by the recipient. The output force may result inmechanical vibration of the recipient's skull, or in physical movementof the skull about the neck of the recipient. As noted above, in certainembodiments, active transcutaneous bone conduction device 200 deliversthe output force to the skull of the recipient via direct contact ofactuator 260 with the recipient's bone. Actuator 260 may be made of abiocompatible piezoelectric material as detailed herein.

FIG. 3A illustrates the conversion of an input sound signal into amechanical force for delivery to the recipient's skull in accordancewith embodiments of active transcutaneous bone conduction device 200. Atblock 302, a sound signal 207 is received by the device of the presentinvention. In certain embodiments, the sound signal is received viamicrophones. In other embodiments, the input sound signal is receivedvia an electrical input. In still other embodiments, a telecoilintegrated in, or connected to, active transcutaneous bone conductiondevice 200 may be used to receive the sound signal.

At block 304, the sound signal received by active transcutaneous boneconduction device 200 is processed by the speech processor inelectronics module 204. As explained above, the speech processor may besimilar to speech processors used in acoustic hearing aids. In suchembodiments, speech processor may selectively amplify, filter and/ormodify the sound signal. For example, the speech processor may be usedto eliminate background or other unwanted noise signals received byactive transcutaneous bone conduction device 200.

At block 306, the processed sound signal is provided to implantablecomponent 250 as an electrical signal. At block 307, implantablecomponent 250 converts the electrical signal into a mechanical forceconfigured to be delivered to the recipient's skull so as to illicit ahearing perception of the sound signal.

As noted above, embodiments of the present invention utilize a material,such as a piezoelectric material, that deforms (e.g., expands and/orcontracts) when exposed to an electrical signal. Piezoelectric elementsthat may be used in embodiments of the present invention may comprise,for example, piezoelectric crystals, piezoelectric ceramics, or someother material exhibiting a deformation in response to an appliedelectrical signal. FIGS. 3B-3D schematically depicts this phenomenon.Initially, as depicted in FIG. 3B, the actuator 308 made ofpiezoelectric material is not subjected to any electrical signal. Theactuator 308 thus has a length L₁ and a thickness W₁, as may be seen inFIG. 3B. Then, an electrical signal is applied to the actuator 308having a first polarity, as depicted with respect to actuator 308 inFIG. 3C. This causes a deformation in the actuator 308 in response tothe application of the electric signal. Specifically, as may be seen,the length of the actuator 308 expands from L₁ and the width of theactuator contracts from W₁ at least away from the ends. Next, theelectrical signal applied to the actuator 308 has a polarity opposite tothat applied with respect to FIG. 3C. This is depicted with respect toactuator 308 in FIG. 3D. As may be seen, the length of the actuator 308in FIG. 3D has contracted from L₁ and the width of the actuator 308 inFIG. 3D has expanded from W₁.

It is noted that in some embodiments, there is no polarity reversal ofthe electrical signal. That is, the electrical signal is applied in abinary manner. If the electrical signal applied has a polarity asdepicted with respect FIG. 3C, the actuator 308 will expand from itslength L₁ and/or contract from its width W₁ without charge (i.e., theactuator 308 depicted in FIG. 3B). If the electrical signal applied hasa polarity as depicted with respect to FIG. 3D, the actuator 308 willcontract from its length L₁ and/or expand from its width W₁ withoutcharge. Removal of the electrical signal returns the actuator 308 to itslength L₁ and/or its width W₁ without charge. It is further noted thatin some embodiments, combinations of the application of an electricalsignal applied in a binary manner and the application of the electricalsignal with reversing polarity may be utilized.

It is noted in some embodiments, upon the application of an electricalsignal, the length of the actuator 308 may stay the same and only thewidth changes or the width may stay the same and only the lengthchanges. Also, in some embodiments, the width and the length bothincrease and decrease with the application of a charge with a givenpolarity.

FIG. 4 illustrates one embodiment of the present invention in which anactive transcutaneous bone conduction device 400 includes an externaldevice 440 and an implantable component 450 that is implanted beneaththe various tissue layers shown. In some embodiments of the presentinvention, the external device 440 corresponds to the external devices140 and 240 detailed above, and the implantable component 450corresponds to the implantable components 150 and 250 detailed above. Asmay be seen, the implantable component 450 includes actuator 408 that isin direct contact with the outer surface of the recipient's skull. Thatis, the actuator 408 is in substantial contact with the recipient's bone136 such that vibration forces from the actuator 408 are communicatedfrom actuator 408 to the recipient's bone 136. It is noted that in someembodiments, there may be one or more thin non-bone tissue layersbetween actuator 408 and the recipient's bone (bone tissue) while stillpermitting sufficient support so as to allow efficient communication ofthe vibration forces generated by actuator 408 to recipient's bone 136.

In the embodiment illustrated in FIG. 4, transmitter coil 406 ofexternal device 440 transmits inductance signals to receiver coil 416 inan implantable housing 454 of implantable component 450. Implantablehousing 454 may correspond to receiver module 254 detailed above. Anelectronics assembly (not shown) contained in implantable housing 454then generates electrical signals (by outputting the signals received byreceiver coil 416 and/or processing/amplifying the signals received byreceiver coil 416) which are conducted via electrical leads 456 toactuator 408, whereupon actuator 408 vibrates upon receipt of thosesignals. It is noted that in other embodiments of the present invention,the actuator 408 may be positioned with such proximity to theimplantable housing 454 that electrical leads 456 are not present, aswill be described in greater detail below.

In an exemplary embodiment of the present invention, the actuator 408 ismade of/includes a material that expands and/or contracts in response toan electrical signal delivered via electrical leads 456 to the actuator408. In this exemplary embodiment, this material is exposed to tissue(including bone 136, muscle 134 and/or fat 128, which are covered byskin 132) and/or body fluids of the recipient, as may be seen in FIG. 4.Further, in this exemplary embodiment, the material is a piezoelectricmaterial.

By ‘exposed to tissue and/or body fluids,’ it is meant that a hermeticbarrier is not present between the piezoelectric material and the tissueand/or body fluids that would substantially inhibit leaching of elementsand/or compounds of the piezoelectric material into the tissue and/orbody fluids. In this regard, embodiments where the material that deformin response to an electrical signal is in direct contact with the skull(e.g., no barrier is interposed between the material and the skull)permits the impartation of vibrational energy resulting from thedeformation of the deformable material directly from the deformablematerial to the skull. By ‘directly from the deformable material to theskull,’ it is meant that the vibrations do not pass through anintermediate component, such as a hermetic layer or hermetic housing toreach the skull.

In an exemplary embodiment, the piezoelectric material forming actuator408 is a titanate, such as, for example, barium titanate (BaTiO₃,hereinafter “BTO”) and/or strontium titanate (SrTiO₃, hereinafter, STO).It is noted that non-biocompatible piezoelectric materials such as leadzirconate titanate (hereinafter PZT), which contains lead, should onlybe implanted in a human when hermetically shielded from human tissueand/or body fluids. Accordingly, an embodiment of the present inventionincludes an actuator 408 made from piezoelectric material substantiallydevoid of non-biocompatible substances in general and lead and/or PZT inparticular. In some embodiments utilizing biocompatible materials toform actuator 408, improved acoustic coupling of the actuator 408 to thebone and, therefore, improved efficiency and performance is achievedbecause the piezoelectric material of the actuator need not be separatedfrom the tissue and/or body fluids of the recipient by a hermeticbarrier. This may provide higher efficiency vis-à-vis performance of theactive transcutaneous bone conduction device in which such an actuatoris used, not to mention enabling relatively simpler, smaller and/or lessexpensive actuator designs. The coupling between the bone of therecipient and the actuator may result in less loss of energy than if theactuator were placed in a housing.

In yet other exemplary embodiments, the piezoelectric material formingactuator 408 may be lithium niobate (LiNbO₃) and/or lithium tantalate(LiTaO₃). In some embodiments, these materials may enhanceosseointegration of the actuator to the skull.

In an exemplary embodiment of the present invention, such as in anembodiment where the piezoelectric material substantially comprises BTO,the piezo coefficient of the piezoelectric material used in the actuator408 is 460 pC/N and/or has an acoustic impedance of 20 Mrayl (20·10⁶N·s·m⁻³). Accordingly, some embodiments utilize a piezoelectric materialhaving an acoustic impedance that more closely matches that of humanbone. In some such embodiments, this reduces the mismatch between theacoustical impedance of the actuator and the skull bone, therebyreducing energy losses at the boundary between the piezoelectricmaterial and the bone.

More specific exemplary features of exemplary actuators that may be usedas actuator 408 will now be described.

As noted above, in an exemplary embodiment of the present invention, aportion of the actuator 408 is exposed to tissue and/or body fluids ofthe recipient. In one embodiment of the present invention as may be seenin FIG. 5A, there is an actuator 508A corresponding to an embodiment ofactuator 408 that is substantially entirely made from/substantiallyentirely comprises biocompatible materials in general and piezoelectricmaterials in particular. In one such exemplary embodiment, thepiezoelectric material(s) is BTO and/or STO. By way of example, such anactuator 508A may be in the form of a plate made of a piezoelectricmaterial such as BTO and/or STO. The actuator 508A may be in the form ofa ceramic. It may be cut from a single crystal of BTO and/or STO.Various crystal structures may be utilized in some embodiments. In someembodiments, the piezoelectric material forming actuator 508A may bedoped with other biocompatible components, such as those that mayfurther enhance osseointegration, as will be detailed below. As may beseen by way of example, the actuator is substantially a monolithiccomponent.

In another embodiment of the present invention as may be seen in FIG.5B, there is an actuator 508B corresponding to an embodiment of actuator408 that, as with actuator 508A, is substantially entirely madefrom/substantially entirely comprises biocompatible materials. However,the actuator 508B is a composite actuator comprising two layers 509 and510 (or more layers which are not shown). In one such exemplaryembodiment, one or more of the layers 509 and 510 are piezoelectricmaterials such as BTO and/or STO. In other embodiments of the presentinvention, one of the layers 509 and 510 is made of a piezoelectricmaterial, and the other layer is made of a non-piezoelectric materialsuch as titanium. With respect to the embodiment depicted in FIG. 5B,the layer 510 is a piezoelectric material and layer 509 is titanium. Asmay be seen, the piezoelectric material of layer 510 is exposed totissue of the recipient (bone 136, etc.). In an alternate embodiment,the layer 509 is a piezoelectric material and layer 510 is titanium, thepiezoelectric material of layer 509 still being exposed to tissue of therecipient.

In another embodiment of the present invention as may be seen in FIG.5C, there is an active component 552 comprising an actuator 508C that,as with actuator 508A, is substantially entirely made from/substantiallyentirely comprises biocompatible materials in general and piezoelectricmaterials in particular. However, the piezoelectric material(s) encasecounterweight 511 (or may partially encase counterweight 511). In anexemplary embodiment, counterweight 511 may be a solid homogeneous massof biocompatible material and/or may be a housing of biocompatiblematerial housing a mass of non-biocompatible material (the housingforming a hermetic seal between the tissue and/or body fluids of therecipient and the non-biocompatible material). As may be seen, thepiezoelectric material of actuator 508C is exposed to tissue of therecipient (bone 136, etc.) It is noted that in some embodiments, element551 may instead be an implantable housing corresponding to implantablehousing 454 detailed above.

In another embodiment of the present invention as may be seen in FIG.5D, there is an implantable component 550 comprising an implantablehousing 554, which may correspond to implantable housing 154 and/or 454detailed above, and an actuator 508D that, as with actuator 508A, issubstantially entirely made from/substantially entirely comprisesbiocompatible materials in general and piezoelectric materials inparticular. However, as may be seen, implantable housing 554 isinterposed on actuator 508D. In such embodiments, electrodes or the likemay extend from implantable housing 554 to provide electrical signals tothe piezoelectric materials of actuator 508D. As may be seen, thepiezoelectric material of actuator 508D is exposed to tissue of therecipient (bone 136, etc.)

As referenced above, embodiments of the present invention include anactuator, such as actuator 508A of FIG. 5A, that includes piezoelectricmaterial that is osseointegrated into the recipients skull. In anexemplary embodiment, the piezoelectric material is doped with orotherwise includes biocompatible components that form a biochemical bondto human bone, which in some embodiments is an osseointegrative bond. Insome such embodiments, the doping component is hydroxyapatite and/orstrontium and/or calcium. In an exemplary embodiment, calcium phosphateis used as a doping component. Any suitable material that enhancesosseointegration of the piezoelectric material to the skull may be usedin some embodiments of the present invention.

Some embodiments of the present invention include an actuator having afirst surface formed by the piezoelectric material that is artificiallyroughened to have a first surface roughness. This first surface isadapted to abut and directly contact the recipient's skull. For example,referring to FIG. 5A, the first surface may be the surface of actuator508A that contacts skull 136. The actuator 508A may have a secondsurface also formed by the material, but located away from the firstsurface, such as, with reference to FIG. 5A, surfaces on the left and/orright sides of actuator 508A, and/or the surface on the side of actuator508A opposite the bottom surface. The second surface may have a secondsurface roughness. The first surface roughness of the first surface issignificantly more rough than the second surface roughness of the secondsurface. By significantly more rough, it is meant that the roughness ofthe surface is such that the first surface roughness accelerates theosseointegration of the actuator to the skull at the first surface at arate that is appreciably faster than what would be the case if the firstsurface had a surface roughness corresponding to the second surfaceroughness. In an exemplary embodiment, the first surface roughness isgreater than that which would result from the normal manufacturingprocess of the actuator (e.g., that which would result from molding theactuator into its final form), the surface roughness resulting from thenormal manufacturing process being the second surface roughness.

Some embodiments of the present invention provide an activetranscutaneous bone conduction device in which the implantable componentis absent certain features that are present in other types of activetranscutaneous bone conduction devices. For example, in at least someembodiments of the present invention utilizing the biocompatiblepiezoelectric material, there is no housing or other type of barrier(e.g., coating) that that provides a hermetic barrier between thepiezoelectric material and the tissue and/or body fluids of therecipient. It is noted that some such embodiments may correspond tothose of FIG. 5D or FIG. 5E, where a portion of the piezoelectricmaterial is covered by or partially contained in, respectively, anon-piezoelectric component. In this regard, FIG. 5E depicts an activecomponent 552 including a biocompatible, osseointegrating actuator 508Ethat is made entirely of BTO doped with osseointegrative enhancingcomponents. A housing 552 covers the top and, partially, the sides ofthe actuator 508E. In an exemplary embodiment, the housing 552 issufficiently flexible to at least effectively not impede movement of theactuator 508E. As may be seen, the housing 552 permits the actuator 508Eto directly contact the skull 136.

Also, embodiments of the present invention may be practiced without aseparate bone fixture (e.g., a component that includes a screw screwedinto the skull and mechanically linked to the actuator) or the like toanchor the actuator to the recipient's skull. Instead, byosseointegrating the actuator to the skull, such a bone fixture is notneeded. However, it is noted that in some embodiments, a bone fixturemay be used with the actuator.

FIG. 6A depicts an exemplary embodiment where a coating of biocompatibleand/or bioactive material has been included in the actuator.Specifically, FIG. 6A depicts an actuator 608A made from a piezoelectricmaterial 609A to which a biocompatible coating 610A has been applied. Inthe embodiment of FIG. 6A, the biocompatible coating 610A is a coatingof a material that enhances osseointegration of the actuator 608A to theskull. It is noted that in some embodiments consistent with FIG. 6A, thepiezoelectric material 609A is doped with a component that enhancesosseointegration, as detailed above, while in others, it is not.

It is noted that in other embodiments, the coatings of biocompatibleand/or bioactive material may not enhance osseointegration. For example,the material may be an antibacterial material and/or a material thatinhibits osseointegration. For example, FIG. 6B depicts anotherexemplary embodiment of the present invention, where a coating ofbiocompatible and/or bioactive material has been included in theactuator. Here, the actuator 608B is embedded, at least partially, in arecess 136A surgically cut into the skull 136. Biocompatible coatings610B and 611B have been applied to the piezoelectric material 609B asmay be seen. In the embodiment of FIG. 6B, the biocompatible coating610B is a coating of a material that inhibits osseointegration of thebottom of the actuator 608B to the skull (e.g., silicon), and thebiocompatible coatings 611B are coatings formed from a material thatenhances osseointegration of the sides of the actuator 608B to the skull(e.g. hydroxyapatite). Thus, the actuator 608B expands and contractswith only the tensile and compressive reactive forces created by thesides of the recess in the skull resisting expansion and contraction ofthe actuator. That is, there is reduced (e.g., little to no) reactiveshearing forces that might otherwise be present if the bottom of theactuator 608B was also osseointegrated to the skull.

In an exemplary embodiment, the actuators detailed herein may have acoating of titanium. The coating may be sputter coated onto thepiezoelectric material.

Also, the embodiment of FIG. 6B includes an antibacterial coating 612Bon top of the piezoelectric actuator. It is noted that in thisembodiment, the piezoelectric material 609B is still exposed to tissueand/or body fluid of the recipient because at least one of the coatingsis such that the piezoelectric material 609B is not hermetically sealedfrom the tissue and/or body fluid of the recipient.

FIG. 6C depicts another exemplary embodiment of the present invention,where the actuator 608C substantially comprises piezoelectric material.However, sections 612 of the actuator 608C have been doped withcomponents that enhance osseointegration of the piezoelectric materialto the skull, and section 613 of the actuator has been doped with amaterial that inhibits osseointegration of the piezoelectric material tothe skull. The doping of this embodiment achieves at least similarfunctionality as the respective coatings detailed above with respect toFIG. 6B. Also, the embodiment of FIG. 6C may be doped with anantibacterial component.

It is noted that in embodiments where sufficient osseointegration of thepiezoelectric material can be obtained without coatings/doping,embodiments may include only adding coatings that inhibitosseointegration/doping with components that inhibit osseointegration.In this regard, FIG. 6D depicts an exemplary actuator 608D that includesa layer 610B of osseointegrating material on the piezoelectric material609D, and FIG. 6E depicts an exemplary actuator 608E with a section 613doped with an osseointegration inhibiting component. The coating anddoping of these embodiments achieve at least similar functionalities asthe respective coating and doping detailed above with respect to FIG.6B.

It is noted that in other embodiments, the various coatings and/or dopedsections may be located at other locations in the actuator than thosejust detailed providing that such placement permits embodiments of thepresent invention to be practiced.

Embodiments of the present invention include a method of implanting anactuator in a recipient. In an exemplary embodiment, the actuatorcorresponds to any of the actuators disclosed herein, such as, forexample, actuator 408 of FIG. 4. Initially, access to an interior of therecipient is surgically obtained. This may entail cutting through therecipient's skin to access the recipient's skull. Next, the interior ofthe recipient is surgically prepared for implantation of the actuator.This may entail removing a certain amount of bone tissue from therecipient to provide a recess, such as recess 136A described above withrespect to FIG. 6B, for the actuator. In a subsequent step, the actuatoris implanted within the recipient, such that the material that deformsin response to an electrical signal delivered thereto is exposed totissue and/or body fluid of the recipient. In an exemplary embodiment,the actuator is placed such that the material is in direct contact withthe skull of the recipient, such as, for example, is depicted in FIG.6C. In an alternate embodiment of this method, the action of implantingthe actuator within the recipient includes positioning the actuator inthe recipient's middle ear or in the recipient's cochlea such that thefirst material is in direct contact with one or more structures of therecipient's ossiclular chain and/or the recipient's cochlea. Furtherembodiments of a system resulting from such a method and variationsthereof are discussed in greater detail below.

Some additional features of some embodiments of the present inventionwill now be described.

Referring back to FIG. 5A, there is an implanted actuator 508A that isplaced directly onto bone 136 without preparing a recess in the bone forthe actuator 508A, where the implanted actuator 508A has osseointegratedto the bone 136, at least with respect to the bottom surface of theactuator 508A. During use, when an electrical signal is applied toactuator 508A, actuator 508A expands and/or contracts to impart a forcein the vertical direction represented by arrow 590A. Vibrational energygenerated via the expansion and/or contraction is imparted into the bone136 due to the biochemical bond between the actuator 508A and the bone136. In an alternative embodiment, still referring back to FIG. 5A,during use, when an electrical signal is applied to actuator 508A,actuator expands and/or contracts to impart a force in the horizontaldirection represented by arrow 590B. Vibrational energy generated viathe expansion and/or contraction is imparted into the bone 136 due tothe biochemical bond between the actuator 508A and the bone 136.

It is noted that in some embodiments, actuators 508A may also expandand/or contract to impart force in the directions of both arrows 590Aand 590B.

Referring now to FIG. 6B, where the actuator has been placed into arecess 136A in bone 136, and the actuator has osseointegrated to thebone 136 at desired locations, which may be established as detailedabove, when an electrical signal is applied to actuator, the actuatorexpands and/or contracts to impart force in the horizontal directionrepresented by arrow 590C. Vibrational energy generated via theexpansion and/or contraction is imparted into the bone 136 due to thebiochemical bond between the actuator and the bone 136. It is noted thatin some embodiments, the actuator may also expand and/or contract toimpart forces in directions normal to arrow 590C in addition to orinstead of directions parallel to arrow 590C.

In another embodiment of the present invention, there is an implantedactuator at least partially implanted in a recess of the skull (e.g., anactuator as depicted in FIG. 6B) that is a composite component thatincludes a counterweight/countermass and/or a non-osseointegratingcomponent. The non-osseointegrating component is made of a material thatinhibits osseointegration of that component to bone. A strata ofpiezoelectric material such as BTO and/or STO is attached to thenon-osseointegrated component, this strata sandwiching thenon-osseointegrating component with the counterweight/countermass. Asjust noted, this actuator may be placed at least partially into a recessin bone, such that at least the strata of piezoelectric material and atleast a portion of the non-osseointegrating component are located in therecess. Over time, the actuator osseointegrates to the bone at desiredlocations of the strata of piezoelectric material. During use, when anelectrical signal is applied to the strata of piezoelectric material,the strata expands and/or contracts to impart forces in a verticaldirection, relative to the skull (e.g., with respect to, for example,FIG. 6B, normal to the direction of arrow 590C). Vibrational energygenerated via the expansion and/or contraction is imparted into thebone. It is noted that in some embodiments, the strata may also expandand/or contract to impart forces in horizontal directions (e.g., in thedirection of arrow 590C of FIG. 6B) in addition to or instead ofvertical directions.

In yet another embodiment of the present invention, there is an actuatorin the form of a composite component that includes a first strata and asecond strata of piezoelectric material such as BTO and/or STOsandwiching a non-osseointegrated component. As detailed above, thenon-osseointegrating component may be made of a material that inhibitsosseointegration of that component to bone. The actuator may be placedat least partially into a recess in bone. Over time, the actuatorosseointegrates to the bone at desired locations of the strata ofpiezoelectric material which may be established as detailed above.During use, when an electrical signal is applied to the strata ofpiezoelectric material, the strata expands and/or contracts to impartcounter-opposing forces. That is, the strata move relative to oneanother away from one another. Vibrational energy generated via theexpansion and/or contraction is imparted into the bone.

FIG. 7 depicts a bone fixture assembly 708 that is part of apercutaneous bone fixture device 701 according to an exemplaryembodiment of the present invention. Percutaneous bone fixture device701 includes a screw-shaped bone fixture 702 and a skin-penetratingabutment 704. Percutaneous bone fixture device 701 may be used as partof a transcutaneous bone conduction device and/or as part of a hybridbone conduction device. By “hybrid bone conduction device,” it is meantthat the device has the functionality of both a percutaneous boneconduction device and a transcutaneous bone conduction device, asexplained in greater detail below.

Bone fixture 702 may be made of any material that has a known ability tointegrate into surrounding bone tissue (i.e., it is made of a materialthat exhibits acceptable osseointegration characteristics). In oneembodiment, the bone fixture 702 is made of titanium. The fixtureincludes a main body 706 with an outer screw thread 703 which isconfigured to be screwed into the skull of the recipient.

The main body 706 of the bone fixture 702 may have length sufficient tosecurely anchor the bone fixtures into the skull without penetratingentirely through the skull. The length of the main body 706 maytherefore depend on the thickness of the skull at the implantation site.In one embodiment, the main bodies of the fixtures have a length that isno greater than 5 mm, measured from the planar bottom surface 707 of theflanges 709 to the end of the distal region of the bone fixture 702(this limits and/or prevents the possibility that the main body 706might be screwed completely through the skull). In another embodiment,the length of the main body is from about 3.0 mm to about 5.0 mm.

The distal region of bone fixture 702 may be fitted with self-tappingcutting edges formed into the exterior surface of the fixture. Furtherdetails of the self-tapping features that may be used in someembodiments of bone fixtures used in embodiments of the presentinvention are described in International Patent Application WO 02/09622.In an exemplary embodiment, increased stability to the attachmentbetween the bone fixture assembly 708 and the abutment 704 is providedas detailed in U.S. Patent Application Publication No. 2009/0082817.

Abutment 704 extends from the bone fixture 702 through muscle, fat andskin of the recipient so that a coupling apparatus of an external devicemay be attached thereto, as described in greater detail below.

In the exemplary embodiment, the bone fixture assembly 708 functions asan actuator, and includes a band or tube of piezoelectric material 710A(or other material that deforms when exposed to an electric signal)extending about the outer diameter of the main body 706 of the bonefixture 702. The outer diameter of the band or tube 710A may fall withinthe outer diameter of threads 703. Alternatively, a band or tube ofpiezoelectric material may extend beyond the outer diameter of threads703, as depicted in FIG. 7. In other embodiments, the band or tube ofpiezoelectric material may be located so that the band or tube onlycontacts the surface of the bone instead of being embedded in the boneas depicted in FIG. 7 (e.g., the band or tube acts as a stop to preventfurther insertion of the bone conduction device into the skull when theband or tube contacts the skull, much in the same manner that flanges709 operate as detailed above). Functionally, the embodiment of FIG. 7may function as an active transcutaneous bone conduction device in asimilar manner to the embodiment detailed above with respect to FIG. 6C.This is because the band or tube 710A is implanted within the skull ofthe recipient as a result of screwing the bone fixture into the skull.Functionally, the embodiment where the band or tube of piezoelectricmaterial is located above the skull on the surface of the skull (notshown) may function as an active transcutaneous bone conduction devicein a similar manner to the embodiment detailed above with respect toFIG. 5A. This is because the band or tube is implanted above the skullof the recipient as a result of screwing the bone fixture 702 into theskull.

Electrical leads (not shown) extend from the piezoelectric material 710Athrough the bone fixture 702 and through the abutment 704 to an externaldevice outside the recipient. In this regard, the bone fixture assembly708 functionally corresponds to actuator 408 of FIG. 4 and theelectrical leads that extend from the piezoelectric material 710Afunctionally correspond to electrical leads 454 of FIG. 4. However,instead of the electrical leads being connected to an implantablehousing 454 as is detailed with respect to FIG. 4, the electrical leadsare connected to an external device that may be, for example, mounted onabutment 704. The electrical leads may contain connectors that permitthe electrical leads to be easily disconnected from the external devicemounted on abutment 704. In some embodiments, the connectors may bequick connect-disconnect connectors that automatically connect anddisconnect from the external device when the external device is mountedon abutment 704 and removed from abutment 704, respectively.

The external device used with the embodiment of FIG. 7 may include atleast some of the components included in implantable housing 454 andexternal device 440 such that operation of the bone fixture assembly 708as an actuator may be accomplished in a similar manner as the operationof actuator 408 of FIG. 4. That is, by extending electrical leads fromthe piezoelectric material 710A through the skin of the recipient to anexternal device, much of the functionality of the components ofimplantable housing 454 can be obtained by components in the externaldevice. For example, the power source to energize the piezoelectricmaterial may be located entirely outside the recipient. Also, somefunctionality of the implantable housing 454 and/or the external device440 may no longer be needed. For example, a receiver coil need not beimplanted in the recipient because percutaneous electrical leads may beused to communicate with the bone fixture assembly 708.

As noted above, embodiments consistent with that of FIG. 7 may be usedin a hybrid bone conduction device. During use of such a hybrid device,an external percutaneous bone conduction device is attached to abutment704 (or variation of abutment 704) as is, by way of example, detailedU.S. patent application Ser. No. 12/177,091 assigned to Cochlear Limitedor U.S. patent application Ser. No. 12/167,796 assigned to CochlearLimited or U.S. patent application Ser. No. 12/167,851. Thepercuntaneous bone conduction device includes a vibratory element, suchas an electromagnetic actuator and/or a piezoelectric actuator, thatvibrates. Because the percutaneous bone conduction device is connectedto the abutment 704, vibrations from the percutaneous bone conductiondevice are transferred via the abutment 704 to the bone fixture assembly708 and then into the bone 136 in a manner analogous to the operation ofa traditional percutaneous bone conduction device.

In an exemplary embodiment, the hybrid bone conduction device impartsvibrational energy to bone of the recipient via the piezoelectricmaterial 710A and the external percutaneous bone conduction deviceattached to abutment 704. In some embodiments, the piezoelectricmaterial 710A is used to generate vibrations at a lower frequency and/ora higher frequency than those generated by the external percutaneousbone conduction device, and/or visa-versa. In other embodiments, insteadof or in addition to this, both the piezoelectric material 710A and theexternal percutaneous bone conduction device generate vibrations overfrequency ranges that overlap. In yet other embodiments, in stead of orin addition to this, the piezoelectric material 710A and the externalbone conduction device are used to generate vibrations during different(separate or overlapping) temporal periods. The hybrid bone conductiondevice may be controlled to generate vibrations from the piezoelectricmaterial 710A and/or the external percutaneous bone conduction device ina manner that improves hearing enhancement over that which may beachieved by using only the piezoelectric material 710A or the externalpercutaneous bone conduction device.

It is noted that in some embodiments, the actuators detailed herein maybe in the form of a circular plate or rod made from BTO and/or STO. Fora maximum thickness of a plate of 30 mm, the outer diameter of the platemay be between 10 to 80 mm. For a maximum thickness of a plate of 20 mm,the outer diameter of the plate may be between 5 to 80 mm. For a maximumthickness of a plate of 10 mm, the outer diameter of the plate may bebetween 2 to 5 mm. For a minimum thickness of a plate of 0.15 mm, theouter diameter of the plate may be between 2 to 20 mm. For a minimumthickness of a plate of 0.3 mm, the outer diameter of the plate may bebetween 2 to 60 mm. For a minimum thickness of a plate of 0.5 mm, theouter diameter of the plate may be between 2 to 80 mm. Similardimensions may be used in the case of a rod.

Also, in an exemplary embodiment, the actuator according to someembodiments herein may be in the form of a hollow tube. For a tube of alength of 1 to 70 mm having an outer diameter of less than 78 mm, theinner diameter may be less than 70 mm. For a tube of a length of 1 to 70mm having an outer diameter of greater than 2 mm, the inner diameter maybe greater than 0.8 mm. FIG. 8 details exemplary dimensions for someexemplary embodiments of an actuator in the form of a disk made from BTOand/or STO, the shaded boxes corresponding to dimensions of someembodiments.

An embodiment of the present invention includes utilizing an actuator asdisclosed herein and/or variations thereof to provide vibrationsdirectly or indirectly to other parts of the anatomy of the recipientother than the skull of the recipient that will in-turn produce auditorystimulation for the recipient. For example, referring to FIG. 9, in anexemplary embodiment, there is a middle-ear hearing prosthesis 1100including an actuator 1108 including material (e.g., BTO and/or STO)that deforms when subjected to an electrical signal according to any ofthe embodiments described herein and variations thereof. The deformingmaterial of actuator 1108 is directly attached to the cochlea 115, asmay be seen. In an exemplary embodiment, the deforming material of theactuator is attached to the oval or round window. The attachment may beformed by direct integration of the material of the actuator to thetissue of the oval or round window and/or through the use of a couplingimplanted along with the actuator (e.g., a mechanical coupling, abiocompatible adhesive, etc.). Similar to the embodiments disclosedherein relating to a bone conduction device, the middle-ear hearingprosthesis of FIG. 9 includes an external device 1140 and an implantablecomponent 1150. The external device 1140 functions in much the same wayas one or more of the other external devices detailed above. Theimplantable component 1150 also functions in much the same way as one ormore of the other implantable components detailed above. However, theoperations of these components are tailored for use in a middle-earhearing prosthesis (i.e., where the actuator is located in themiddle-ear) as opposed to a bone conduction device (where the actuatoris located on and/or in the skull), and thus the processing aspects ofthe system may be different. Implantable component 1150 includes ahousing 1154 that includes, for example, a telecoil and other componentsthat provide an electrical signal to actuator 1108 in a manner analogousto the components that provide electrical signals to the other actuatorsdetailed above. Accordingly, while not shown in FIG. 9, actuator 1108 isin electrical communication with housing 1154 via, for example,electrical lead or the like. It is noted that in other embodiments, theexternal device 1140 and/or the housing 1154 of the implantablecomponent may be located at other locations than that depicted in FIG.9.

FIG. 10 depicts an alternate embodiment of a middle-ear hearingprosthesis 1100 also including an actuator 1108. The deforming materialof the actuator is instead attached directly to one or more members ofthe ossiclular chain, as may be seen. In the embodiment of FIG. 10, theactuator 1108 is attached to the malleus 112. Actuator 1108 may beattached in the same manner or similar manner as detailed above withrespect to attachment of the actuator 1108 to the cochlea.

In an alternate embodiment, an actuator having deformable material asdetailed herein and/or variations thereof is located inside the cochlea.In an exemplary embodiment, the actuator provides mechanical stimulationto the hair fibers of the cochlea. In some such embodiments, thedeforming material of the actuator is thus configured to be implantedinside a recipient's cochlea and configured to be mechanically coupledto the inside of the recipient's cochlea.

FIG. 11A depicts an actuator 1108A that may be used with a middle-earhearing prosthesis. The actuator includes a housing 1112, which may bemade of titanium or zinconium, including an electrical feedthrough 1114.Electrical contact pins 1116 of feedthrough 1114 permit electricalcommunication from the outside of the housing 1112 to the inside of thehousing 1112. Leads 1118 connect the pins 1116 to an electromagneticvibrator 1120 hermetically sealed in the housing 1112. When theelectromagnetic vibrator 1120 is energized, actuator rod 1119 moves in aaxial and/or a radial direction. Actuator rod 1119 is connected to oneor more members of the ossicular chain or to the cochlea, therebyimparting mechanical stimulation to those components.

As just noted, the housing 1112 is hermetically sealed to protect theelectromagnetic vibrator 1120 from body fluids of the recipient. In anembodiment of the present invention, as depicted in FIG. 11B, there isan actuator 1108B utilizing piezoelectric material. This embodiment issimilar to that of FIG. 11A, except that the electromagnetic actuator1120 is replaced with a piezo stack 1122 comprising a plurality of disksmade of piezoelectric material stacked one on top of the other andsecured together in a stack. Leads 118 connect the pins 116 offeedthrough 1114 to the piezo stack 1122. When an electrical signal isapplied to the piezo stack 1122, the piezoelectric material of the stack1122 deforms, and the actuator rod 1119, which is mechanically coupledto piezo stack 1122, moves in an axial and/or a radial direction as aresult of deflection of the piezoelectric material of the piezo stack1122. In a middle-ear implant utilizing actuator 1108B, actuator rod1119 is connected to one or more members of the ossicular chain or tothe cochlea.

If the piezo stack 1122 is made from biocompatible material such as BTO,such as the embodiment depicted in FIG. 11B, the housing 1112 need nothermetically seal the piezo stack 1122 from the body fluids of therecipient, in contrast to the housing 1112 of actuator 1108A.Accordingly, the housing 1112 serves only to protect the piezo stack1122 from physical damage resulting from applied force. Alternatively orin addition to this, the housing 1112 may provide structural support tothe components of the actuator 1108B, such as supporting the feedthrough1114 above the piezo stack 1122 as shown.

FIG. 11C depicts an actuator 1108C that utilizes a piezo stack 1124 thatsubstantially conforms to piezo stack 1122 of FIG. 11B, and alsoutilizes piezoelectric material that is biocompatible. However, actuator1108C does not utilize a housing 1112 to protect that piezo stack 1122.Instead, the piezo stack 1124 is directly attached to one or moremembers of the ossicular chain or to the cochlea. Because there is nohousing, a feedthrough is not necessary. Instead, an electrical contactpin support 1126 supports electrical contact pins 1128. Pins 1128conduct electricity to the piezoelectric material of the piezo stack1124. Upon application of an electrical signal to the piezo stack 1124,the piezoelectric material of the piezo stack 1124 deforms, therebyimparting vibrations to the recipient's middle ear.

It is noted that in some embodiments of the present invention, actuators1108B and/or 1108C may be connected to the skull to transmit vibrationsto the skull.

In yet another alternate embodiment, piezoelectric material implanted inthe recipient is a utilized as a transducer. In an exemplary embodiment,it is used as part of a sound capture device such as an implantablemicrophone. By way of example, referring to FIG. 12, which is identicalto FIG. 1 detailed above except for the absence of sound capture device126 and the addition of implanted microphone 1170 (the details of whichwill be provided below), the sound wave 107, being a wave that diffusesas it travels through the atmosphere, also impinges upon the outer skin132 of the recipient. Energy from that impinging sound wave travelsthrough the skin to the implanted piezoelectric material 1172 of theimplanted microphone 1170. This energy deforms the piezoelectricmaterial (typically compressing the piezoelectric material resultingfrom the pressure applied to the material), causing the piezoelectricmaterial to generate an electrical charge in response to thisdeformation. While not shown in FIG. 12, the piezoelectric material isin electrical communication with an implanted sound processor ofimplantable component 150 that receives electrical signals from thepiezoelectric material resulting from the generated electrical charge ina manner that may be analogous to how a sound processor receiveselectrical signals from a conventional microphone. The sound processorprocesses those signals in a manner that may be analogous to how thesound processor processes the electrical signals from a conventionalmicrophone. It is noted that there may be one or more intermediatecomponents between the piezoelectric material and the sound processor,as is detailed above, for example, with respect to intermediatecomponents between a microphone and a sound processor. In some suchalternate embodiments, this permits a fully implantable hearingprosthesis to be provided to a recipient in a manner analogous to suchsystems utilizing conventional implanted microphones.

In yet another alternate embodiment, the transducer made frompiezoelectric material implanted in the recipient is an implantableelectricity generator. That is, the piezoelectric material is used togenerate electricity to power implanted electrical components or tocharge a power storage device, such as a battery. In an exemplaryembodiment, the piezoelectric material is implanted beneath the skin ofthe recipient in such a manner that pressure may be repeatedly appliedto the material through the skin. In alternate embodiments, pressure maybe applied via the use of muscles. For example, referring to FIG. 13,which depicts an arm 1200 of a recipient, piezoelectric material 1254 isimplanted in the recipient between bone 1236 and skin 1232. Morespecifically, piezoelectric material 1254 is implanted between biceps1234 such that when the biceps 1234 are used during the normal course ofevents, pressure is applied to the piezoelectric material 1254. Thispressure causes the piezoelectric material 1254 to deform, therebygenerating electricity. That is, because the piezoelectric material 1254is positioned adjacent to muscle tissue such that it deforms in responseto contraction of the muscle tissue, the piezoelectric material 1254generates electricity as a result of the normal use of the recipient'sarm. The piezoelectric material is in electrical communication viaelectrical leads 1256 with an implanted power storage device, such as abattery, and/or any other implanted component that is powered byelectricity, such as any one or more of the components detailed herein(not shown in FIG. 13). Further by example, piezoelectric material 1254maybe implanted between or against leg muscles, etc., or any othermuscle that will permit the piezoelectric material to generateelectricity that may be usefully harnessed.

In some embodiments of the present invention, the piezoelectric materialis directly attached to muscle tissue by direct integration of thematerial of the muscle tissue and/or through the use of a couplingimplanted along with the piezoelectric material (e.g., a mechanicalcoupling, a biocompatible adhesive, etc.). In some embodiments, thepiezoelectric material may be formed in a manner that it surrounds someor all of the muscle tissue such that a separate connector or bond isnot needed. In other embodiments, the material may be positioned suchthat it is trapped between muscle tissue and or other tissue such thatit will not effectively move from a desired location, also alleviatingthe need for a separate connector or bond.

In an exemplary embodiment, the implantable microphone system detailedabove that also utilizes implanted piezoelectric material is also usedto generate electricity, or, more specifically, the electricity that isgenerated by the implantable microphone is harnessed in a manner beyondusing the electricity to carry a sound signal to a signal processor(e.g., is used to charge a battery). In some embodiments, the hearingprosthesis utilizing the implanted microphone system is configured toswitch between the functionality of an implantable microphone and apower generation device. This switch to a power generation device may bedone, for example, when a recipient does not need to use the hearingprosthesis to hear.

An embodiment of the present invention also includes utilizing theimplanted piezoelectric material to generate an electrical chargethereon. This generated electrical charge is used to enhanceosseointegration of the piezoelectric material to bone. By way ofexample, the recipient or caregiver may massage his or her skin at alocation adjacent the implanted piezoelectric material, therebydeforming the implanted piezoelectric material such that an electricalcharge may be established therein. To facilitate this, the boneconduction device may configured such that is may be switched (eithermanually or automatically) to a mode that ensures that the electricalleads to the piezoelectric material or other pertinent electricalconnection do not conduct the electrical charge from the material.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to persons skilledin the relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. A hearing prosthesis comprising: an actuator including a materialthat deforms in response to an electrical signal and that is adapted to,upon implantation in a recipient, transmit vibrations representative ofa sound signal to an organ of the recipient, wherein the material isconfigured to be at least partially directly exposed to at least one ofbody tissue or fluid of the recipient. 2-4. (canceled)
 5. The hearingprosthesis of claim 1, wherein the material is substantially devoid oflead zirconate titanate. 6-8. (canceled)
 9. The hearing prosthesis ofclaim 1, wherein the material is doped with a second material thatenhances osseointegration of the material with the skull of therecipient. 10-14. (canceled)
 15. The hearing prosthesis of claim 1,wherein a surface of the material has a coating thereon, and wherein thecoating is configured to substantially prevent osseointegration of thecoated portions.
 16. The hearing prosthesis of claim 1, wherein theactuator is adapted to be implanted such that the material directlycontacts the skull of the recipient.
 17. The hearing prosthesis of claim1, wherein the actuator includes: a first surface formed by thematerial, the first surface being adapted to directly contact the skullof the recipient, the first surface having a first surface roughness;and a second surface formed by the material located away from the firstsurface, the second surface having a second surface roughness, the firstsurface roughness being more rough than the second surface roughness.18. The hearing prosthesis of claim 1, wherein the first surfaceroughness is significantly more rough than the second surface roughnesssuch that the first surface roughness accelerates the osseointegrationof the actuator to the skull at the first surface relative to that whichwould take place if the first surface had the second surface roughness.19-20. (canceled)
 21. The hearing prosthesis of claim 1, wherein thematerial is a material that enhances osseointegration.
 22. The hearingprosthesis of claim 1, wherein the hearing prosthesis is a boneconduction device.
 23. The hearing prosthesis of claim 22, wherein thehearing prosthesis is an active transcutaneous bone conduction device.24. (canceled)
 25. The hearing prosthesis of claim 22, wherein thehearing prosthesis comprises a percutaneous bone fixture deviceincluding a bone fixture and a skin-penetrating abutment, and whereinthe actuator is attached to the bone fixture. 26-27. (canceled)
 28. Theprosthesis of claim 1, wherein the material is mechanically attached toat least one of (i) one or more structures of the ossicular chain of therecipient, (ii) a cochlea of the recipient or (iii) a skull bone of therecipient, and wherein the material is at least partially directlyexposed to at least one of body tissue or fluid of the recipient. 29.The prosthesis of claim 1, wherein the prosthesis is configured to beimplanted inside a cochlea of the recipient and configured to bemechanically coupled to the inside of the cochlea. 30-33. (canceled) 34.A transducer, comprising: a material that at least one of generateselectricity when deformed or deforms when exposed to electricity,wherein the material is adapted to be at least partially exposed to atleast one of body tissue or fluid of the recipient.
 35. The transducerof claim 34, wherein the transducer is an implantable microphone, andwherein the material is adapted to deform in response to ambient soundwaves impinging upon the skin of the recipient.
 36. The transducer ofclaim 34, wherein the transducer is an implantable electricitygenerator, and wherein the material is adapted to be positioned adjacentto muscle tissue and deform in response to contraction of the muscletissue.
 37. The transducer of claim 36, wherein the transducer is inelectrical communication with a power storage device.
 38. A method ofimparting vibrational energy to bone, the method comprising: deforming adeformable material in response to an electric signal applied thereto;and imparting vibrational energy resulting from the deformation of thedeformable material directly from the deformable material to the bone.39-41. (canceled)
 42. The method of claim 38, wherein: the deformablematerial is at least partially embedded in a recess surgically cut intoa skull of the recipient; and the deformation of the deformable materialimparts at least one of tensile or compressive forces onto sidewalls ofthe recess.
 43. The hearing prosthesis of claim 22, wherein the hearingprosthesis comprises a bone fixture, wherein the actuator is attached tothe bone fixture.
 44. The hearing prosthesis of claim 22, wherein thehearing prosthesis comprises a bone fixture, wherein the actuator isattached to the bone fixture, and wherein the actuator extends about thebone fixture.
 45. The hearing prosthesis of claim 22, wherein thehearing prosthesis comprises a percutaneous bone fixture deviceincluding a bone fixture, a skin-penetrating abutment, and a secondactuator mounted to the abutment such that, in use, the second actuatoris located outside the recipient, and wherein the actuator is attachedto the bone fixture such that, in use, the actuator is located in therecipient.
 46. The transducer of claim 34, wherein: the transducer is atransducer of a middle ear hearing prosthesis configured such that, inuse, the material is in direct contact with at least one of an ossiclesof a recipient or a cochlea of the recipient such that deformation. 47.The transducer of claim 34, wherein: the transducer is an actuator of amiddle ear hearing prosthesis configured such that the material deformswhen exposed to electricity so as to drive the prosthesis and thus evokea hearing percept.
 48. The transducer of claim 47, wherein: the materialforms a piezoelectric stack, wherein the actuator of the middle earhearing prosthesis is configured such that the piezoelectric stack isnot hermetically sealed from an ambient environment of the actuator. 49.A method, comprising: working a muscle adjacent the transducer of claim34, and generating electricity using the transducer, wherein the workingof the muscle deforms the material, thus generating the electricity, andthe material is at least partially exposed to body tissue or fluid ofthe recipient.